drm/panel-simple: Update validation warnings for eDP panel description

Do not give a warning for the eDP panels if the "bus_format" is
not specified, since most eDP panels can support more than one
bus formats and this can be auto-detected.
Also, update the check to include bpc=10 for the eDP panel.

Signed-off-by: Rajeev Nandan <rajeevny@codeaurora.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1624726268-14869-5-git-send-email-rajeevny@codeaurora.org